Documentation: update header filename in CodingStyle

pr_info() and pr_debug() are in linux/printk.h, not linux/kernel.h.
Last updated is unnecessary, we have git for that.

Signed-off-by: Roland Kammerer <dev.rck@gmail.com>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Harry Wei <harryxiyou@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/CodingStyle

@@ -659,7 +659,7 @@ There are a number of driver model diagnostic macros in <linux/device.h>
 which you should use to make sure messages are matched to the right device
 and driver, and are tagged with the right level:  dev_err(), dev_warn(),
 dev_info(), and so forth.  For messages that aren't associated with a
-particular device, <linux/kernel.h> defines pr_debug() and pr_info().
+particular device, <linux/printk.h> defines pr_debug() and pr_info().
 
 Coming up with good debugging messages can be quite a challenge; and once
 you have them, they can be a huge help for remote troubleshooting.  Such
@@ -819,6 +819,3 @@ language C, URL: http://www.open-std.org/JTC1/SC22/WG14/
 Kernel CodingStyle, by greg@kroah.com at OLS 2002:
 http://www.kroah.com/linux/talks/ols_2002_kernel_codingstyle_talk/html/
 
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-Last updated on 2007-July-13.
-